1. Field of the Invention
This invention relates generally to rotary drill bits and is more particularly directed to a removable ball plug for inserting or removing ball bearings from a ball bearing race in the class of rotary drill bits wherein a race for ball bearings is formed in the journal and on the interior of a cutter cone which, upon the insertion of a plurality of ball bearings serves to retain the rotating cutter cone in operating disposition on the journal on a leg of a rotary drill bit.
2. Description of the Prior Art
The following prior art was noted in the course of a preliminary investigation concerning the invention of this application;
______________________________________ U.S. Pat. No. Inventor Issued ______________________________________ 1,779,587 Childs October 28, 1930 2,676,790 Turner April 27, 1954 3,862,762 Millsap January 28, 1975 3,989,315 Murdoch November 2, 1976 4,014,595 Dolezal March 29, 1977 4,211,453 Johansson July 8, 1980 ______________________________________
Of the above U.S. patents, the Turner U.S. Pat. No. 2,676,790 and Murdoch U.S. Pat. No. 3,989,315 illustrate earlier attempts to provide removable ball plugs in roller bits that incorporate ball bearings for purposes that include the retention of a cutter cone on a journal. As will be recognized upon a thorough consideration of the respective disclosures, each of the patents represent an unduly complicated structure for providing the desired result. Each of the references requires at least three elements for obtaining the desired result. One present method of securing the ball plug is to fill in the outer portion of the ball hole by welding. Manufacturers tend to shallow up the outer portion of the ball plug hole to require less weld material and less change of heat build-up. Welding may also lead to destruction of the heat treated bearing race and seals. The shallow weld-filled hole may wear off during drilling with consequent loss of ball plug and retainer ball bearings and pre-mature rock bit failure.